1. Field of the Invention
This invention pertains to a fall arrestor and lockdown device for vertical lift doors, particularly single membrane fabric vertical lift doors.
2. Description of the Prior Art
Many applications, such as aircraft hangars, today require large vertical lift doors. This need has been addressed by large single membrane fabric vertical lift doors. However, in the absence of proper safety equipment, such doors have the potential for rapid falls caused by cable or lift belt breaks. It is therefore important that such doors have fall arrestors which are responsive to cable or lift belt breaks. It is also important to realize that such fall arrestors ordinarily are activated only in unexpected cable or lift belt break situations. Such intermittent activation can lead to latent inoperability, such as contamination from debris due to lack of use, which is not detected prior to an unexpected cable or lift belt break.
Some prior art devices use friction methods for fall arrestor systems. These arrestor systems damage the door jamb and/or door beams thereby leading to extended down-time and costly repair. Further, they can allow the door leaf to continue falling after engagement by sliding on debris found in the jambs due to low maintenance or high contamination.
Additionally, it is important for such vertical lift doors to be automatically locked upon closing, so that surreptitious entrance cannot be gained by merely lifting the lower crossbar of the single membrane fabric vertical lift door.
It is therefore an object of this invention to provide a fall arrestor for vertical lift doors, particularly single membrane fabric vertical lift doors.
It is therefore a further object of this invention to provide a fall arrestor for vertical lift doors, particularly single membrane fabric vertical lift doors, which is simple in construction and reliable.
It is therefore a further object of this invention to provide a fall arrestor for vertical lift doors, particularly single membrane fabric vertical lift doors, which positively and reliably engages the door jamb without damage to the door jamb.
It is therefore a further object of this invention to provide a fall arrestor for vertical lift doors, particularly single membrane fabric vertical lift doors, which is periodically cycled to aid in detecting latent inoperability.
It is therefore a further object of this invention to provide a fall arrestor for vertical lift doors, particularly single membrane fabric vertical lift doors, which can be reset quickly after repair of a failed cable or lift belt.
It is therefore a further object of this invention to provide a lockdown device for vertical lift doors, particularly single membrane fabric vertical lift doors.
It is therefore a final object of this invention to provide a fall arrestor and lockdown device for vertical lift doors, particularly single membrane fabric vertical lift doors, which is relatively inexpensive to manufacture.
These and other objects are attained by a fall arrestor and lockdown device which is integral with the guide system on the bottom beam of the door and rigidly attached thereto. The fall arrestor and lockdown device includes a spring activated pin device which is attached by mechanical linkage to a rotatable cable or lift belt tension sensing arm. A wire rope or cable passes through the sensing arm. Alternatively, a lift belt can be attached directly to the arm. When the cable or lift belt is xe2x80x9cchargedxe2x80x9d (tension is applied to the cable or lift belt), the sensing arm rotates thereby moving the linkage, retracting the pin and compressing the coil spring. The pin retracts to clear apertures that are placed in the door jamb according to door-width parameters. In the event that the cable or lift belt breaks, the force of the compressed coil spring overcomes the lift applied by the cable or lift belt in the sensing arm and consequently the pin extends. With pressure applied by the coil spring to the pin, the pin is forced outwardly against the door jamb tracking until it reaches an aperture in the jamb. The pin then fires into the aperture where it then comes to rest upon hitting the edge of the side frame. Upon activation of the arrestor system, the beam fall due to cable or lift belt failure is arrested.
The lockdown feature is accomplished when the door reaches its bottom height. The cable or lift belt will lose tension due to the transfer of load from the cable to the ground. This load transfer allows the sensing arm to articulate or rotate in a controlled manner. The pin thereby extends into a jamb placed into the side frame thereby locking the door. This locking provides resistance to unwanted intrusion as well as resistance to beam lift due to catenary forces form wind loading to the fabric. Upon reinitiation of the door cycle, the tension from the cable or lift belt again charges the arrestor system retracting the pin for the arrestor mode.